Method and apparatus for closing or sealing containers of paper, cardboard, or the like carton-forming material



Jan. 12, 1960 l-j. ZERLIN 2,920,432

METHOD AND APPARATUS FOR CLOSING 0R SEALING CONTAINERS OF PAPER. CARDBOARD. OR THE LIKE CARTON-FORMING MATERIAL Filed Feb. 11, 1958 I Fig. 1

3 Sheets-Sheet l Fig. 2 1 16 15 Z 7 o 6 l zfl Jan. 12, 1960- H. ZERLIN 2,920,432

METHOD AND APPARATUS F CL NG OR SEALING CONTAINERS OF" PAPER. RD RD. OR THE CARTON-F0 LIKE RMING MATERIAL Filed Feb, 11, 1958 3 Sheets-Sheet 2 Jan. 12, 1960 H. ZERLIN 2,920,432

vm'mon AND APPARATUS FOR CLOSING OR SEALING CONTAINERS OF PAPER. CARDBOARD. OR THE LIKE CARTON-FORMING MATERIAL Filed Feb. 11, 1958 3 Sheets-Sheet 3 Fig. 4- y a 76 1a 15 4 13 0 2 17 LIT 7 O memp H ZerL bib I I I United States Patent METHOD AND APPARATUS FOR CLOSING OR SEALING CONTAINERS OF PAPER, CARD- BOARD, OR THE LIKE CARTON-FORMING MATERIAL Hans Zerlin, Dusseldorf, Germany, assignor to Jag'enberg- Werke Aktie.-Ges., Dusseldorf, Germany Application February 11, 1958, Serial No. 714,658 Claims priority, application Germany February 15, 1957 Claims. (Cl. 53-371) The present invention relates broadly to the art of container manufacture.

More particularly, the invention relates to apparatus for closing, including sealing, in a liquid tight relationship, containers of paper, cardboard, or the like cartonforming material. More specifically, the invention relates to apparatus for closing or sealing containers of the type in which portions of the walls above the filling level are folded todefine a gable or roof-type closure and in which opposite walls engage along a closing line and a closure flap-forming portion on one of these walls is folded over the other in overlapping'relation, and the closure is sealed by application of heat and pressure.

Still more specifically, this invention relates to apparatus for closing containers of the type referred to in which the upper portion of opposite walls are placed in engagement, bent at an angle and then crimp-pressed at right angles to the longitudinal axis of the container.

In containers of this character, generally used for receiving milk, it is necessary that the closure be liquid tight, of simple construction and of good appearance. Furthermore, the closure construction must be such that once the carton is open and a portion of the contents have been dispensed, the carton can be reclosed with suificient eflicacy to effectively protect the remaining contents against the ingress of dust or other foreign particles.

Container closures, especially for milk cartons are generally efiected by forming a gable or roof-like structure out of the wall portion of the container that extends above the filling level. This structure being accomplished by prefolding opposite walls inwardly and then folding the other pair of opposite walls together until they engage, the latter walls having an impregnating and binding medium thereon which is capable of adhesively uniting contacting wall portions together under the application of heat and pressure.

In prior filed application, Serial Number 602,007 filed August 3, 1956, now US. Patent No. 2,888,794, in the name of Gunther-Meyer Jagenberg and entitled Method and Apparatus for Filling, Folding and Closing Containers of Paper, Cardboard or the Like Carton-Forming Material, there is disclosed the general type container with which this invention is concerned.

In effecting adequate closure of containers of this type, special means are employed to ensure tightness and strength of the closure in that the fiat closure fold is subjected to a stiffening profiling procedure. One type of known container closure is stifi'ened by bending over the engaging wall portions or what could be termed flattened closure portions, at an angle, and pressing this bent over section together at right angles to the longitudinal axis of the container to form a strengthening rib or crimp.

The procedure of clamping the closure fold by the pressing jaws and subsequently bending the upper end of the closure fold over at an angle strained the material of which the container is constituted to such a degree as to destroy the fiber because the tensions created by this bending and clamping and exerted between the individual lines of the closure fold could not be relieved because relative movement between the layers of the closure fold was prevented due to their being clamped between the pressing jaws. The stresses and strains and thus deforming tensions caused by this operation in combination with the subsequently applied high clamping pressure give rise to undesirable material destruction, which in turn results in leakage in thefinished closure. Additionally, when a closure of this type is open, portions of the closure fold separated completely from the container body along the line of destroyed fibers, thus completely eliminating the possibility of reclosing the container after a portion of its contents had been removed.

It is, therefore, an object of the present invention to eliminate the aforegoing disadvantages, and accordingly the formation and pressing or sealing of the closure fold is effected so that the upper portion of the flatly folded closure is first bent over in an angular relationship without applying any appreciable pressure thereto and then the crimping pressure is applied at right angles to the longitudinal axis of the container. Proceeding in accordance with this method, assures that the angulation of the upper portion of the folded closure occurs without destroying any material'fibers, since the extent of the de formingpressure is adjusted merely to the pressure necessary for eifecting the angular bend; In other WOIdS, no other forces affect this portion of the closing or sealing operation, so that the individual layers of the closure fold have the opportunity of re-aligning themselves and thus relieving any tensions which may occur. In carrying out the aforedescribed method, the invention utilizes pressing jaws or tools, one of which can be termed a countertool and the other movable ja'w means. The countertool which can also be designated a stationary jaw, is provided with an angle-shaped recess, and with a folding edge directly in continuance of this recess. When a container has been introduced between the jaws, the upper end of the closure fold rests against this folding edge, so that this edge effects, in cooperation with the pressing jaw means the angular bending of the upper part of the closure fold before the lower portion ofthe closure fold is clamped against the associated countertool or fixed jaw by the movable jaw means.

It is a further object of the invention to providea container closing mechanism of the type including the immediately aforementioned jaws, in which the upper surface of the angle shaped recess in the countertool or jaw lies essentially in the plane of movement of the movable jaw means, the latter consisting of two portions, a leading portion comprising a pressing jaw and a lagging portion comprising a crimping tool. Further, the included angle formed between the upper and lower surfaces of the angle-shaped recess in the countertool is less than This construction of the recess in the countertool has the advantage that the leading edge of the leading portion of the movable jaw means is conformed in slope angle to the cooperating pressing surface of the counter jaw which prevents shifting of the pressing jaws when pressure is applied and also pulls the leading edge of the leading portion of the movable jaw means into the recess of the countertool or jaw means when a pressure is exerted that is Vertical to the direction of the main pressure being exerted by the leading portion of the movable jaw means.

v In order to reduce the normally comparatively high pressure which must be exerted by the leading portion or" a movable jaw means to press the lower portion of the closure fold against the corresponding surface of the angle-shaped recess in the countertool or jaw, thev invention provides an arrangement in which the'free edge of the lower surface of the angle-shaped recess in the countertool is provided with a ridge which projects outwardly beyond the adjacent pressing surface of the recess and assures that the lower portion of the container closure is effectively clamped and also prevents the lagging portion of the movable jaw means from pushing the partly bent closure fold partway out of the grasp of the jaws.

It is to be pointed out that when working with containers of thin-walled material it is necessary to take additional care to prevent formation of folds or channels in the container material during crimping of the bentover portion of the closure by the action of the lagging portion of the pressing jaw means. This danger exists because, due to the thinness of the container material, the bent-over portion of the material of the closure does not completely fill out the space between the upper surface of the leading portion of the pressing jaw means and the corresponding or superposed surface of the angleshaped recess in the countertool or jaw. Therefore, to avoid formation of folds or channels, the present invention has for an object to provide an arrangement in which the effective pressing surface of the lagging portion of the pressing jaw means is offset or recessed in such a manner that the leading edge, in the direction of the pressure to be exerted, can slide underneath the upper part of the bent-over closure fold of thin material prior to the exertion of crimping pressure.

A further condition for obtaining a smooth even, and I level, pressed or sealed closure fold is the provision of free play of the tools or jaws in their guideways. To prevent an undue increase in this play among the various movable members of the jaws, which could occur when the jaws shift away from each other under the influence of the pressure that is exerted and thus permit material to be pressed into the spaces thus formed, a pressure that acts vertical to the direction of movement of the movable jaw means is exerted and increases as the jaws come together.

Further and more specific objects will be apparent from the following description taken in connection with the accompanying drawings, in which:

Figures 1-4 are fragmentary views, partly in longitudinal section and partly in elevation, illustrating the head structure that incorporates the jaw or tool means and shows the individual working steps in carrying out the method of the invention.

Figure illustrates the relative positions of the tools corresponding to the wor 'ng step shown in Fig. 3, but with a container closure of thin material insufficient to fill out the space between the tools.

Figure 6 illustrates the right-hand end view of the sealing device.

Figure 7 illustrates the upper portion of a folded and sealed container closure.

In Figure 1 there is illustrated a supporting column l on which is fixed a stationary guideway 2 to which is fastened a countertool or fixed element or jaw 3. The guideway 2 is provided with a channel therethrough in which is supported for longitudinal movement a slide 4 which includes an outer head structure 4' that accommodates the pressing jaw means. The pressing jaw means are constituted by two parts or element 5 and 6 being respectively the leading portion and lagging portion of the movable pressing jaw means. A link or pullbar 7 is pivotally attached to the rear end of the slide 4 at one end and at its other end to a lever 8 via pivot connection 10. Lever 8 is a shank or short arm portion extending at an angle to the axis of a hand lever 9, so that movements of the hand lever 9 about shaft or pivot 11 are transmitted via shank 8 and link 7 to the slide 4 to reciprocate the same and thus move the head 4 and tool elements 5 and 6 toward and away from the countertool or stationary jaw 3 depending on whether the hand lever 9 is swung downwardly or upwardly respectively.

The leading portion or tool element 5 of the movable jaw means is slidably disposed in a recess in the lower part of the head 4'. A coil spring 12 is biased between the rear end of tool element 5 and a leaf-spring-like resilient abutment 14. The tool element 5 has less vertical dimensions than the recess in the head and within the recess and supen'mposed on the tool element 5 is the tool element 6 or lagging portion of the movable jaw means. Tool element 6 is of fiat plate-like configuration and longer than tool element 5. The rear end of tool element 6 rests against a leaf-spring-like resilient abutment or holder 13. The holders 13 and 14 also shown in Fig. 6 permit a minimum shifting of the tool elements 5 and 6 in the direction of their sliding movement within the recess whenever an undue pressure is exerted and thus prevent the application of excessive stress or strain, with resultant possible damage to the tool elements.

The head portion 4' carries on its upper surface a rigidly fixed arm 15, that extends back toward the fulcrum or pivot 11, carried by the stationary guideway 22. The arm 15 supports on its free end a roller 16 that cooperates with an inclined cam surface 17 suitably mounted in the upper surface of the guideway 2. When the slide 4 moves toward column 1 to bring the tool elements 5 and 6 toward the countertool or fixed jaw 3, roller 16 rolls up the inclined cam surface 17 to exert a pressure on the tool elements 5 and 6 that is vertical to their pressing direction, so as to decrease the amount of free play between the tool elements.

Heating elements 18 are imbedded in the head portion 4 of the slide so as to transmit heat to the tool elements 5 and 6 and the countertool or stationary jaw 3, by conduction. It being understood that the material of the upper portion of the container that defines the folded closure is provided with a heat and pressure activatable adhesive.

As especially shown in Figdlre l the countertool or stationary jaw 3 provided with an angle-shaped recess or undercut 19 including an upper generally horizontal surface 23 and a lower angular surface 24. The angle defined between these two surfaces is about 75. The forward edge 20 of the upper surface 23 of the recess defines a folding edge and the lower edge of the lower surface 24 of the recess terminates in a protruding ridge or head 21. Further, the upper surface 23 of the recess lies in the plane of movement of the upper surface of the tool element 6.

To conform to the shape of recess 19 in the countertool or fixed jaw 3, the effective pressing surface of pressing tool element 5 has its leading face 25 sloped at an angle of about 75 relative to its upper surface, and a groove 22 is formed in this face to correspond to the protruding ridge or head 21 on the lower edge of surface 24 of recess 19. The effective pressing surface 26 of tool element 6 is offset in such manner that if the container is of thin walled material, as shown in Figure 5, and the material to be crimped does not fill the space between the undersurface 23 of recess 19 and the upper surface of tool element 5, then the forward edge of lagging tool element 6 can slide underneath that part of the folded closure which is to be crimped so as to prevent the formation of folds or channels in the closure.

In order to simplify construction and assembly of the parts of what can be termed a sealing head, and particularly to simplify transmission of movement of hand lever 9 to the pressing jaws, the parts are so arranged and constructed, as indicated previously, that countertool or pressing jaw 3 including its recess 19, is a stationary and fixed tool, while the pressing tool elements 5 and 6 achieves the angled bending of the upper portion of the closure fold 27, the clamping of the lower portion of the closure fold, and also the crimping at right angles to the vertical axis of the container of the bent-over upper portion of the closure fold, are the movable elements or jaws, and accomplish these functions in one movement of lever 9.

The individual phases of the bending, pressing and crimping presses are clearly shown in Figures 1 to 4. From the position shown in Figure 1, in which the slide 4 has been displaced away from pivot 11 so that the jaws are open, and a container with its closure prefolded in overlapped condition about its upper portion, as shown in the said aforementioned prior filed application, Serial Number 602,007, is introduced into the space between the jaws in such manner that the upper edge of the closure bars against folding edge 20, hand lever 9 is moved downwards from the position of Figure l to cause the slide 4 to move rearwards and the pressing tool elements 5 and 6 to move in the direction toward countertool or fixed jaw 3. During this movement, tool element 5, the leading portion ofthe movable jaw means, bends the upper portion of closure fold 27 at an angle as shown in Figure 2, before the lower portion of the closure fold 27 is clamped between the pressing surface 24 of fixed jaw 3 and the leading surface 25 of tool element 5. The final clamping of the lower portion of the closure fold 27 between the surfaces 24 and 25, is effected when the movable tool element 5 reaches the position shown in Figure 3, which causes the protruding rib or bead 21 on the lower edge of surface 24 of the recess 19 to become effective and to assure an exact positioning of the folded closure for the application of further pressing and crimping actions without the tools exerting any undue pressure. Figure 3 also illustrates that after the lower portion of' closure fold 27 has been clamped between the jaw means including the cooperation of ridge 21 and groove 22 and before the crimping pressure that is to be applied to the bent-over upper end of the closure fold becomes effective, the surfaces of the recess in the tool 3 and the leading surfaces of tool elements 5 and 6 define an enclosed pressing space around the closure fold 27, which prevents the material to be pressed from shifting in any directionat the beginning of or during the pressing or crimping procedure.

The continued forward movement of slide 4 compresses spring 12 and also causes lagging tool element 6 to become effective so that its leading edge moves in under surface 23 of-the recess in countertool 3 and crirnps the bent-over portion of closure fold 27 to form the crimp 28 as shown in Fig. 4. This crimp is clearly shown in Figure 7 which illustrates a container which has been closed and sealed in accordance with the present invention.

It is believed clear, therefore, that the invention discloses a mechanism for closing containers made of paper or the like carton-forming material, where the upper portion of the container wall portion folded flatly and overlapping once is bent at an angle and the portion so bent has clamping pressure applied at a right angle to the longitudinal axis of the container. The mechanism is at :a single work station having pressure tool means comprised by a fixed element 3 having an angular recess 19 defining a pressing space and terminating in a forward edge for folding over the upper portion of a closure flap. For cooperation with this recess, the mechanism includes a movable jaw means consisting of two relatively movable parts including a pressing jaw 5 having a leading end 22 for folding over the upper portion of the closure flap and a crimping tool 6 having a leading end for crimping the folded portion of the closure flap at a right angle to the longitudinal axis of the container. Means constituting the guideway 2 support, the slide 4 and thus the pressing jaw and crimping tool for movement toward and away from said fixed element so as to permit insertionof a closure flap within the recess when the pressing jawand crimping tool are moved away from the fixed element 3. Also, means in the form of the link and lever mechanism and handle 10, due to the connection with slide 4 and thus parts 5 and 6 carried thereby, move the pressing jaw and crimping tool towards said fixed element with the leading end of the crimping tool in trailing relation with respect to the leading end of the pressing jaw to initially fold over said flap and clamp the same into said'recess land to thereafter advance said crimping tool relative to said pressing jaw to crimp said flap. Thus, the folding, clamping and crimping of the closure flap is effected at the single work station in asingle stroke of the cooperating two parts of the movable jaw means toward the fixed element due to the relative movement between said two parts.

What is claimed is:

1. In mechanism for closing containers made of paper or the like carton-fonning material, where the upper portion of the container wall portions, folded flatly and overlapping once, is bent at an angle and the portion so bent has clamping pressure applied at a right angle to the longitudinal axis of the container, the improvement comprising a single work station having a pressure tool means comprised by a fixed element having an angular recess defining a pressing space and terminating in a forward edge for folding over the upper portion of the closure flap, a movable jaw means consisting of two relatively movable parts including apresslng jaw having a leading end for folding over. the upper portion of the closure flap, and a crimping tool having a leading end for crimping the folded portion of'the closure flap at a rightlangle to the longitudinal axis of the container, means supporting said pressing jaw and crimping tool for movement toward and away from said fixed element so as to permit insertion of a closure flap within said recess, and means for moving said pressing jaw and crimping tool toward said fixed element, with the leading end of the crimping tool in trailing relation with respect to the leading end of the pressing jaw to initially fold over a flap positioned on said recess and clamp the same in said recess and to thereafter advance said crimping tool relative to said pressing jaw to crimp said flap whereby the folding, clamping and crimping of the closure flap. is effected at said station in a single stroke of the cooperating two parts of the movable jaw means toward said fixed element due to the relative movement between said two parts.

2. Mechanism for closing and sealing paperboard containers of the type including a gable closure above a filling level having opposite wall portions folded into engagement and with one of said opposite wall portions overlapping, the other to provide a closure fold extending transversely of the container and prolonging the longitudinal median axis thereof, said mechanism comprising cooperable relatively movable heat and pressure applying jaw means adapted to receive a container closure fold therebetween, one of said jaw means having an angleshaped recess therein adapted to define a pressing space, said recess having a rear pressing surface and an upper generally horizontal guiding surface extending toward the other jaw means and terminating in a folding edge, whereby upon relative movement of said jaw means toward each other the upper portion of an inserted closure fold is first bent over at an angle to the container axis by said edge before the lower portion of said closure fold is clamped between said jaw means, the pressing jaw means having the angle-shaped recess therein being a stationary jaw, the other jaw means being mounted for movement toward and away from the stationary jaw and including two superposed pressing tool elements, the lowermost element having a leading clamping surface adapted to bend over the upper portion of the. closure fold at an angle in cooperation with said folding edge and to apply clamping pressure against the lower portion of the closure fold and said other tool element being constructed and arranged to crimp the upper portion of the closure fold at right angles to the longitudinal axis of the, container, and both saidtool elements effecting said bending, clamping, and crimping in one stroke of movement toward said stationary jaw.

3. Mechanism as claimed in claim 2 in which the angle-shaped recess in the stationary jaw and the leading faces of the respective tool elements define a completely enclosed pressing space after the lower tool element is moved to a position to clamp the lower portion of the closure fold while the upper movable tool element is in a position relative to the stationary jaw such that the crimping pressure to be exerted by said upper tool element is ineffective.

4. Mechanism for closing and sealing paperboard containers of the type including a gable closure above a filling level having opposite wall portions folded into engagement and with one of said opposite wall portions overlapping the other to provide a closure fold extending transversely of the container and prolonging the longitudinal median axis thereof, said mechanism comprising cooperable relatively movable heat and pressure applying jaw means adapted to receive a container closure fold therebetween, one of said jaw means having an angleshaped recess therein adapted to define a pressing space, said recess having a rear pressing surface and an upper generally horizontal guiding surface extending toward the other jaw means and terminating in a folding edge, whereby upon relative movement of said jaw means toward each other the upper portion of an inserted closure fold is first bent over at an angle to the container axis by said edge before the lower portion of said closure fold is clamped between said jaw means, the pressing jaw means having the angle-shaped recess therein being a stationary jaw, the other jaw means being mounted for movement toward and away from the stationary jaw and including two superposed pressing tool elements, the lowermost element having a leading clamping surface adapted to bend over the upper portion of the closure fold at an angle in cooperation with said folding edge and to apply clamping pressure against the lower portion of the closure fold and said other tool element being constructed and arranged to crimp the upper portion of the closure fold at right angles to the longitudinal axis of the container, both said tool elements effecting said bending, clamping, and crimping in one stroke of movement toward said stationary jaw, the surfaces of the stationary jaw defining said angle-shaped recess forming an angle of less than 90 degrees, and said upper guiding surface of the recess extending essentially parallel to the direction of movement of the lower movable tool element.

5. Mechanism as claimed in claim 4 in which the lower terminal edge of the rear pressing surface of the angleshaped recess has a ridge thereon extending forwardly of said pressing surface and the leading face of the lower tool element of the movable jaw means having a groove therein positioned in correspondence with and cooperable with said ridge.

6. Mechanism for closing and sealing paperboard containers of the type including a gable closure above a filling level having opposite wall portions folded into engagement and with one of said opposite wall portions overlapping the other to provide a closure fold extending transversely of the container and prolonging the longitudinal median axis thereof, said mechanism comprising cooperable relatively movable heat and pressure applying jaw means adapted to receive a container closure fold therebetween, one of said jaw means having an angle shaped recess therein adapted to define a pressing space, said recess having a rear pressing surface and an upper generally horizontal guiding surface extending toward the other jaw means and terminating in a folding edge, whereby upon relative movement of said jaw means toward each other the upper portion of an inserted closure fold is first bent over at an angle to the container axis by said edge before the lower portion of said closure fold is clamped between said jaw means, the pressing jaw means having the angle-shaped recess therein being a stationary jaw, the other jaw means being mounted for movement toward and away from the stationary jaw and including two superposed pressing tool elements, the lowermost element having a leading clamping surface adapted to bend over the upper portion of the closure fold at an angle in cooperation with said folding edge and to apply clamping pressure against the lower portion of the closure fold and said other tool element being constructed and arranged to crimp the upper portion of the closure fold at right angles to the longitudinal axis of the container, both said tool elements effecting said bending, clamping, and crimping in one stroke of movement toward said stationary jaw, means mounting the upper and lower tool elements of the movable jaw so that during the movement of the movable jaw means toward the stationary jaw the lower tool element moves in advance of the upper tool element, and the leading and effective surface of the upper tool element being recessed transversely of its line of movement for applying a crimp in the closure fold.

7. Mechanism for closing and sealing paperboard containers of the type including a gable closure above a filling level having opposite wall portions folded into engagement and with one of said opposite wall portions overlapping the other to provide a closure fold extending transversely of the container and prolonging the longitudinal median axis thereof, said mechanism comprising cooperable relatively movable heat and pressure applying jaw means adapted to receive a container closure fold therebetween, one of said jaw means having an angleshaped recess therein adapted to define a pressing space, said recess having a rear pressing surface and an upper generally horizontal guiding surface extending toward the other jaw means and terminating in a folding edge, whereby upon relative movement of said jaw means toward each other the upper portion of an inserted closure fold is first bent over at an angle to the container axis by said edge before the lower portion of said closure fold is clamped between said jaw means, the pressing jaw means having the angle-shaped recess therein being a stationary jaw, the other jaw means being mounted for movement toward and away from the stationary jaw and including two superposed pressing tool elements, the lowermost element having a leading clamping surface adapted to bend over the upper portion of the closure fold at an angle in cooperation with said folding edge and to apply clamping pressure against the lower portion of the closure fold and said other tool element being constructed and arranged to crimp the upper portion of the closure fold at right angles to the longitudinal axis of the container, both said tool elements effecting said bending, clamping and crimping in one stroke of movement toward said stationary jaw, a support accommodating said stationary jaw, said movable jaw means including {a slide portion guided by said support for movement toward and away from the stationary jaw, and means embodied respectively with the movable jaw means and support for exerting a pressure on said tool elements in a direction approximately vertical to their direction of movement as the tool elements get closer to the stationary jaw whereby any relative play between the tool elements is reduced.

8. Mechanism as claimed in claim 7 in which said movable jaw means includes a head having a recess therein extending toward the stationary jaw, said tool elements being mounted in superposed relation and in sliding engagement within said recess, and resilient supporting means carried at least in part by said head and cooperating with the rear ends of the respective tool elements.

9. Mechanism for closing and sealing paperboard cartons of the type including a closure having opposite wall portions in engagement with one another and with one of said opposite wall portions overlapping the other to define a closure fold extending transversely of the container and prolonging the longitudinal axis thereof, said mechanism comprising a stationary support, said support having a guideway embodied therewith, a slide mounted in said guideway for reciprocable movement, a stationary jaw can'ied by said support, said slide including a head, said head having a recess therethrough extending toward said stationary jaw, a pair of pressing tool elements mounted in superposed relation within said recess, said stationary jaw having an angle-shaped recess extending inwardly from its leading surface including an upper horizontal guiding surface terminating in a forwardly disposed folding edge and a rear generally flat pressing surface, said guiding surface and pressing surface defining an angle less than a right angle, the lowermost one of said pressing tool elements having an upper forward edge adapted to deflect a closure fold inserted between the jaws about the folding edge upon movement of the slide toward the stationary jaw without applying any appreciable pressure to the closure fold and to subsequently apply clamping pressure against the lower portion of the closure fold to clamp it against said rear pressing surface of the angle-shaped recess, and the upper tool element in the recess in the said head having a leading face constructed and arranged to apply a crimp in the outer edge of the bent-over upper end of the closure fold to extend transversely of the longitudinal axis of the container, and means cooperating with said tool elements to cause the lower tool element to move in advance of the upper tool element during movement of the slide toward the stationary jaw whereby the crimping pressure is exerted only after the lower portion of the closure fold has been clamped.

10. Mechanism as claimed in claim 9, in which the leading face of the lowermost tool element has substantially the same angle of slope as the rear pressing surface of the angle-shaped recess, a rib protruding forwards of the lower terminal edge of said rear pressing surface and the leading face of said lower tool element having a groove extending transversely thereof in correspondence with the position of and cooperable with said rib during the application of clamping pressure.

References Cited in the file of this patent UNITED STATES PATENTS 

